Method of and apparatus for grinding a solid in a liquid



y 5, 1964 A. SZEGVARI 3,131,875

I METHOD OF AND APPARATUS FOR GRINDING A SOLID IN A LIQUID Filed Aug. 17, 1961 INVENTUR. ANDREW SZEGVARI Bi /Mm ATTORNEY FIG. 2

United States Patent 3,131,875 METHOD OF AND APPARATUS FOR GRINDING A SOLID IN A LIQUID Andrew Szegvari, 120 Ash St., Akron 8, Ohio Filed Aug. 17, 196i, Ser. No. 132,057 Claims priority, application Japan Sept. 5, 1960 6 Claims. (Cl. 24127) This invention relates to improved apparatus for agitating the grinding elements in grinding equipment of the type shown and described in my U.S. Patent 2,764,359.

The grinding elements are substantially spherical, and all are of substantially the same size. They may be composed of metal, stone, or the like. They are put into motion and then kept in substantially constant motion out of static contact with one another by moving one or more agitator blades horizontally through a mass of them in a vessel. The improvement of this invention is in the shape of the agitator blade or blades and the improved grinding action which results from their use.

The blade is streamlined with a thin forward edge which tapers to a blunt rear edge, its cross section being substantially that of the vertical cross section of a tear drop. It is moved through the grinding elements in the direction opposite to that in which an airfoil moves through the air because the airfoil is shaped to cause minimum agitation of the air, particularly at its rear edge, and it is the function of the agitator blade to cause maximum agitation of the grinding elements, with minimum consumption of energy.

The invention will be further described in connection with the accompanying drawings, in which FIG. 1 is an elevation of an empty grinding vessel equipped with an agitator provided with blades of the invention;

FIG. 2 is an enlarged detail of a corner of the vessel, the grinding elements being much closer together than illustrated, in actual practice; and

FIG. 3 is a section through a blade on the line 33 of FIG. 2, with a schematic showing of how the grinding elements are agitated.

The vessel 5, of S-gallon capacity, contains a large number of steel balls 6, each measuring inch in diameter. The grinding elements may vary in size from fine sandsized particles, e.g. inch in diameter to elements ii; inch in diameter or larger, depending upon the size of the vessel, the nature of the material to be ground, etc. The vessel is filled with these elements to a depth to cover the top blade of the agitator.

The agitator comprises a number of evenly spaced agitator blades 8 which project from the vertical shaft 9 which is adapted to be rotated at a speed of 50 to 300 revolutions per minute, depending upon the material subjected to treatment, the ultimate particle size desired, etc. The outer ends of the blades are spaced about inch (three times an element diameter) from the wall of the vessel to prevent jamming of the elements in that space.

The agitator may be used for dry grinding, or the grinding of a suspension from which the grinding elements quickly settle. It may be used for grinding extremely hard materials, and the rapid grinding of softer materials, and the processing of sensitive materials such as biological preparations, medicinals, and other edible products in which more than a trace of impurities derived from the wall structure of the grinding vessel is objectionable. Thus, it may be used for grinding tungsten carbide, paint pigments, coal, procain penicillin and many, many other materials. Where suitable they may be ground dry, although usually they will be ground in suspension in water or other thinly fluid liquid. The hardness, etc. required in the grinding elements will depend upon the material subjected to treatment. Vessels of several hundred gallons capacity can be used. Several agitators of the type shown, all rotated in the same direction, may be used in a single vessel.

In grinding, the agitator arm is moved with the thin edge forward at a suflicient speed to keep the elements (except those adjacent the bottom and the wall of the vessel) out of static contact with one another. They are suspended in the liquid, and are directed toward each other due to the negative hydrostatic pressure caused by different sides of the same airfoil-shape agitator means. They are in substantially constant motion throughout the grinding operation, bouncing against one another and grinding the material in their respective paths. The action of the elements is more particularly described in said U.S. 2,764,359.

After grinding, the vessel may be tipped to empty its contents, or it may be provided with suitable valve means 10, which may be of the type described in said U.S. 2,764,- 359 which retains the grinding elements in the vessel while permitting the discharge of a liquid suspension or" the ground product.

The invention is covered in the claims which follow.

What I claim is:

1. In apparatus for grinding a solid in a liquid which includes in a vessel, many substantially spherical grinding elements all of substantially the same size, and at least one substantially horizontal elongated element adapted to be rotated about an axis at sufiicient speed for maintaining the grinding element out of static contact with one another, the improvement in which said elongated element is streamlined and has a cross section substantially that of the vertical cross section of a tear drop, with means for moving the elongated element with the thin edge thereof the leading edge, whereby agitation of grinding elements is accelerated immediately to the rear of the elongated element as it is moved through the grinding elements.

2. In the method of grinding by a mass of substantially spherical grinding elements all of substantially the same size which are maintained in substantially constant motion out of static contact with one another in the presence of the material to be ground, by moving therethrough streamlined agitating means which has a cross section substantially that of the vertical cross section of a tear drop, the improvement in which the thin forward edge of the agitating means is moved into the mass of agitating elements as the leading edge thereby spreading a path for the agitating means and following this the blunt edge is moved through the agitating mass whereby violent agitation of the grinding elements is produced immediately to its rear.

3. In the method of grinding by a mass of substantially spherical grinding elements all of substantially the same size and suspended in a liquid, the improvement which comprises moving through the elements streamlined agitating means which has a cross section substantially that of the vertical cross section of a tear drop, with its thin edge forward and by the subsequent passage of the blunt edge through the agitating elements directing them toward one another at the rear of the agitating means as it is moved through the liquid due to the negative hydrostatic pressure caused by the passage of the different sides of the same agitating means through the liquid, and moving the agitating means at a sufficient speed to maintain the grinding elements out of static contact with one another.

4. A grinding or mixing process performed by contacting balls or grinding elements which are part of a liquid system, whereby these elements are moved into contact primarily by producing hydrodynamic flow behind a moving streamlined agitator arm which broadens gradually backwardly from a pointed front edge and has a blunt 7 rear, thereby keeping the elements in substantially constreamlined agitator arm which has a thin forward edge and tapers backwardly to a blunt rear edge, through grinding elements out of static contact with one another in a medium that behaves like a liquid whereby the elements are moved into contact behind the agitator arm primarily because of hydrodynamic flow existing behind the agitator arm and produced by the movement of the agitator arm and thereby kept in substantially constant motion out of static contact with one another.

6. In apparatus for grinding a solid in a liquid which includes a vessel, a liquid in the vessel, many substantially spherical grinding elements all of substantially the same size suspended in the liquid out of static contact with one another, and at least one substantially horizontal elongated element adapted to be rotated about a'ver tical axis for maintaining the grinding elements suspended in the liquid, the improvement in which said elongated element has a cross section substantially that of a tear drop with the thin edge thereof the leading edge and free of all sharp edges to the rear of said leading edge, whereby agitation of the grinding elements is accelerated immediately to the rear of the elongated element primarily by hydrodynamic fiow as the elongated element is moved 10 through the grinding elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,764,359 Szegvari Sept; 25, 1956 15 2,779,752 Vining Jan. 29, 1957 FOREIGN PATENTS 5 1 450,670 Canada Aug. 24, 1948 

2. IN THE METHOD OF GRINDING BY A MASS OF SUBSTANTIALLY SPHERICAL GRINDING ELEMENTS ALL OF SUBSTANTIALLY THE SAME SIZE WHICH ARE MAINTAINED IN SUBSTANTIALLY CONSTANT MOTION OUT OF STATIC CONTACT WITH ONE ANOTHER IN THE PRESENCE OF THE MATERIAL TO BE GROUND, BY MOVING THERETHROUGH STREAMLINED AGITATING MEANS WHICH HAS A CROSS SECTION SUBSTANTIALLY THAT OF THE VERTICAL CROSS SECTION OF A TEAR DROP, THE IMPROVEMENT IN WHICH THE THIN FORWARD EDGE OF THE AGITATING MEANS IS MOVED INTO THE MASS OF AGITATING ELEMENTS AS THE LEADING EDGE THEREBY SPREADING A PATH FOR THE AGITATING MEANS AND FOLLOWING THIS THE BLUNT EDGE IS MOVED THROUGH THE AGITATING MASS WHEREBY VIOLENT AGITATION OF THE GRINDING ELEMENTS IS PRODUCED IMMEDIATELY TO ITS REAR. 